System for controlling rotational direction switchover and for variably controlling rotational speed of motor

Abstract

A system for controlling rotational direction switchover and for variably controlling the rotational speed of a motor comprises a circuit for switching over the rotational direction of the motor, a circuit for supplying rotation driving voltage to the motor thereby to drive it at a speed depending on the rotation driving voltage, a single voltage varying unit for varying voltage continuously, and a control signal generation circuit which receives variable voltage from the voltage varying means to generate a rotational control signal for the rotation driving voltage supplying circuit and further to generate a rotational direction switchover control signal for the switchover circuit. The voltage of the rotation control signal produced by the control signal generation circuit decreasing as the variable voltage approaches a predetermined value, reaching a minimum when the variable voltage coincides with the predetermined voltage, and increasing as the variable voltage goes beyond the predetermined value. The rotational direction switchover control signal is produced by the control signal generation circuit when the variable voltage is substantially the predetermined value.

What is claimed is: 
     
       1. A system for controlling a switchover of rotational directions and for variably controlling the rotational speed of a motor, said system comprising: a motor capable of rotating in both a normal direction and a reverse direction;   means for switching over the rotational direction of said motor;   means for supplying a driving voltage to said motor, said motor rotating at a speed which depends upon the driving voltage;   a single voltage varying means for continuously varying a voltage; and   control signal generating means responsive to a variable voltage from said voltage varying means for generating a rotational control signal and a motor rotation stop signal for controlling said driving voltage supplying means and further for generating a rotational direction switchover control signal for controlling said switchover means, the voltage of said rotation control signal produced by said control signal generating means decreasing as the variable voltage approaches a predetermined value, said rotation control signal reaching a minimum when the variable voltage coincides with the predetermined value, and increasing as the variable voltage goes beyond the predetermined value, the motor rotation stop signal being generated when the variable voltage decreases and reaches substantially the predetermined voltage, and the rotational direction switchover control signal being produced by said control signal generating means when the variable voltage is substantially at said predetermined voltage.   
     
     
       2. A system for controlling a switchover of rotational directions and for variably controlling the rotational speed of a motor, said system comprising: a motor capable of rotating in both a normal direction and a reverse direction;   means for switching over the rotational direction of said motor;   means for supplying a driving voltage to said motor, said motor rotating at a speed which depends upon the driving voltage;   a single voltage varying means for continuously varying a voltage; and   control signal generating means responsive to a variable voltage from said voltage varying means for generating a rotational control signal for said driving voltage supplying means and further for generating a rotational direction switchover control signal for controlling said switchover means,   said control signal generating means comprising a first circuit means comprising:   a first operational amplifier having an inversion input terminal coupled to receive the variable voltage, said first operational amplifier generating an output voltage having a voltage value which decreases and increases in response to an increase and a decrease in the variable voltage, a second circuit means comprising a second operational amplifier having a non-inversion input terminal coupled to receive the variable voltage, said second operational amplifier generating an output voltage having a voltage value which increases and decreases with an increase and a decrease in the variable voltage, and a third circuit means comprising first and second transistors having bases which are respectively connected to the output sides of said first and second operational amplifiers and having emitters which are connected to each other, the output voltage of said first and second transistors being the larger value of the output voltages of said first and second circuit means, said third circuit means supplying the output voltage appearing at the junction of the emitters of said first and second transistors as the rotational control signal supplied to said driving voltage supplying means, the voltage of said rotation control signal produced by said control signal generating means decreasing as the variable voltage approaches a predetermined value, said control signal voltage reaching a minimum when the variable voltage coincides with the predetermined value, and increasing as the variable voltage goes beyond the predetermined value, and the rotational direction switchover control signal being produced by said control signal generating means when the variable voltage is substantially at the predetermined value.   
     
     
       3. A system for controlling a switchover of rotational directions and for variably controlling the rotational speed of a motor, said system comprising: a motor capable of rotating in both a normal direction and a reverse direction;   means for switching over the rotational direction of said motor;   means for supplying a driving voltage to said motor, said motor rotating at a speed which depends upon the driving voltage;   a single voltage varying means for continuously varying a voltage; and   control signal generating means responsive to a variable voltage from said voltage varying means for generating a rotational control signal for said driving voltage supplying means and further for generating a rotational direction switchover control signal for controlling said switchover means, a control signal generating means comprising a first circuit means for generating an output voltage having a voltage value which decreases and increases in response to an increase and a decrease in the variable voltage, a second circuit means for generating an output voltage having a voltage value which increases and decreases with an increase and a decrease in the variable voltage, a third circuit means having an output voltage which is the larger value among the output voltages of said first and second circuit means, said third circuit means supplying its output voltage as the rotational control signal to said driving voltage supplying means, a fourth circuit means for producing an output voltage which assumes a low level when the output voltage of said second circuit means is less than a reference voltage and assumes a high level when said output voltage is more than the reference voltage, the reference voltage being somewhat larger than the output voltage corresponding to the predetermined voltage, and a fifth circuit means for producing the rotational direction switching control signal when the output voltage of said fourth circuit means assumes a high level, the voltage of said rotation control signal produced by said control signal generating means decreasing as the variable voltage approaches a predetermined value, said rotational control signal voltage reaching a minimum when the variable voltage coincides with the predetermined value, and increasing as the variable voltage goes beyond the predetermined value, and the rotational direction switchover control signal being produced by said control signal generating means when the variable voltage is at substantially the predetermined value.   
     
     
       4. A system as claimed in claim 3 in which said control signal generating means further comprises a sixth circuit means for producing an output voltage which assumes a high level when the output voltage of said first circuit means is more than the reference voltage and assumes a low level when said output voltage is less than the reference voltage, and a seventh circuit means for shutting off application of voltage from said rotational driving voltage supplying means to said motor while the output voltages of the fourth and sixth circuit means both assumes a low level. 
     
     
       5. A system as claimed in claim 4 in which said fourth circuit means comprises a third operational amplifier having a non-inversion input terminal applied with the output voltage of said second circuit means and an inversion input terminal applied with the reference voltage, said fifth circuit means comprises a fourth operational amplifier having a non-inversion input terminal applied with the output voltage of said first circuit means and an inversion input terminal applied with the reference voltage, and said eleventh circuit means comprises a transistor circuit for grounding said rotational driving voltage supplying means during a period of time while the output voltages of said fourth and fifth circuit means both assumes a low level.